Vaccine trial participants may show false positives
Patients could face discrimination, other problems
There are a variety of HIV vaccine studies under way, including some that have reached the clinical stage, and they have the potential to produce HIV antibodies that could be seen as false positives on HIV tests, according to a recent study.
"Vaccine constructs are designed to produce an immune response, and these also produce antibodies that are parts of HIV virus and that are the same antibodies that current screening tests are designed to detect," says Marta-Louise Ackers, MD, MPH, a medical epidemiologist for the Division of HIV and AIDS Prevention of the Centers for Disease Control and Prevention in Atlanta.
"We decided to test selected serum samples from vaccine trial participants in the United States with a variety of different screening tests," Ackers says. "Essentially we looked at 490 serum specimens from 461 vaccine recipients, and basically we found that 100 or 20% reacted on at least one serologic screening test."
When investigators followed up those 100 specimens using a Western Blot confirmatory test, they found that 65 of these specimens tested positive, 31 were indeterminate, and four were negative.1 "Then we just reported that among vaccine trial participants, potentially 65 could have been misidentified as HIV-infected," Ackers says. Because vaccine participants undergo extensive testing, including PCR testing and RNA testing, the vaccine investigators monitor their true HIV status.
Insurance screening for HIV poses risk
However, there is always the possibility that these vaccine participants could be tested for HIV during the course of a life or health insurance screening or for some other reason, and they would be at risk for social harms because of their false positive results, Ackers says. For example, a false-positive vaccine participant could be denied health or life insurance coverage or be rejected from blood donation centers. They could even be denied entry to countries in which they would like to travel, Ackers says.
"We need to determine what future solutions are available to us to continue accurate HIV testing when there are a lot of different trials using different constructs going on," Ackers says. "Do we modify the current HIV testing algorithm, or do we create new screening tests?"
Clinicians who treat vaccine participants could help prevent these problems by having the patients notify any companies that intend to screen them for HIV infection that they were involved in an HIV vaccine trial and could have a false positive test result. There have been instances in the past when vaccine participants were turned down from donating blood because of the HIV antibody, and now participants are told by vaccine trial investigators that they won’t be able to donate blood, Ackers says.
"People think the antibody will wane and they won’t be positive anymore, and in some cases that’s true," Ackers adds. "But some remain positive for six to 12 months after vaccination, and there’s not any data on whether they could remain positive for years."
Reference
1. Ackers M-L, Parekh B, Evans TG, et al. HIV seropositivity among uninfected HIV vaccine recipients. Presented at the 9th Conference on Retroviruses and Opportunistic Infections. Seattle; Feb. 25-28, 2002. Poster 294-W.
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